[GOBBLIN-1494]Fix flaky test on HiveSource (#3338)

HiveSourceTest returns 2 watermarks for testGetWorkunitsAfterWatermark instead of 1.
This is due to System.getCurrentTime.millis() returning a different value when comparing against the filesystem last updated filetime. To guard against this, change the test to incorporate the workunit within the watermark by assigning it an earlier creation time, thus implying that the file was modified so it needs to be ingested again.

gobblin-data-management/src/test/java/org/apache/gobblin/data/management/conversion/hive/HiveSourceTest.java

@@ -133,21 +133,30 @@ public void testGetWorkunitsAfterWatermark() throws Exception {
 
     Table table1 = this.hiveMetastoreTestUtils.getLocalMetastoreClient().getTable(dbName, TEST_TABLE_1);
 
+    // Denote watermark to have a past created timestamp, so that the watermark workunit gets generated
+    // This is so that the test is reliable across different operating systems and not flaky to System timing differences
     previousWorkUnitStates.add(ConversionHiveTestUtils.createWus(dbName, TEST_TABLE_1,
-        TimeUnit.MILLISECONDS.convert(table1.getCreateTime(), TimeUnit.SECONDS)));
+        TimeUnit.MILLISECONDS.convert(table1.getCreateTime(), TimeUnit.SECONDS)-100));
 
     SourceState testState = new SourceState(getTestState(dbName), previousWorkUnitStates);
     testState.setProp(HiveSource.HIVE_SOURCE_WATERMARKER_FACTORY_CLASS_KEY, TableLevelWatermarker.Factory.class.getName());
 
     List<WorkUnit> workUnits = this.hiveSource.getWorkunits(testState);
 
-    Assert.assertEquals(workUnits.size(), 1);
+    Assert.assertEquals(workUnits.size(), 2);
     WorkUnit wu = workUnits.get(0);
 
     HiveWorkUnit hwu = new HiveWorkUnit(wu);
 
     Assert.assertEquals(hwu.getHiveDataset().getDbAndTable().getDb(), dbName);
-    Assert.assertEquals(hwu.getHiveDataset().getDbAndTable().getTable(), TEST_TABLE_2);
+    Assert.assertEquals(hwu.getHiveDataset().getDbAndTable().getTable(), TEST_TABLE_1);
+
+    WorkUnit wu2 = workUnits.get(1);
+
+    HiveWorkUnit hwu2 = new HiveWorkUnit(wu2);
+
+    Assert.assertEquals(hwu2.getHiveDataset().getDbAndTable().getDb(), dbName);
+    Assert.assertEquals(hwu2.getHiveDataset().getDbAndTable().getTable(), TEST_TABLE_2);
   }
 
   @Test